Algorithms for detecting atrial arrhythmias from discriminatory signatures of ventricular cycle lengths

Abstract

Detection of arrhythmias is facilitated using irregularity of ventricular beats measured by delta-RR (ΔRR) intervals that exhibit discriminatory signatures when plotted in a Lorenz scatter-plot. An “AF signature metric” is established characteristic of episodes of AF that exhibit highly scattered (sparse) distributions or formations of 2-D data points. An “AFL signature metric” is established characteristic of episodes of AFL that exhibit a highly concentrated (clustered) distribution or formation of 2-D data points. A set of heart beat interval data is quantified to generate highly scattered (sparse) formations as a first discrimination metric and highly concentrated (clustered) distributions or formations as a second discrimination metric. The first discrimination metric is compared to the AF signature metric, and / or the second discrimination metric is compared to the AFL signature metric. AF or HFL is declared if the first discrimination metric satisfies either one of the AF signature metric.

Description

[0001]The present invention relates to detection of atrial arrhythmias, particularly atrial fibrillation (AF) and atrial flutter (AFL) using discriminatory signatures of the ventricular cycle lengths.BACKGROUND OF THE INVENTION[0002]The mechanical events of the heart are preceded and initiated by the electrochemical activity of the heart (i.e., the propagation of the action potential). In a healthy heart, the electrical and mechanical operation of the heart is regulated by electrical signals produced by the heart's sino-atrial (SA) node located in the right atrial wall. Each atrial depolarization signal produced by the SA node spreads across the atria, causing the depolarization and contraction of the atria, and arrives at the atrioventricular (A-V) node. The A-V node responds by propagating a ventricular depolarization signal through the “Bundle of His” of the ventricular septum and thereafter to the “Bundle Branches” and the Purkinje muscle fibers of the right and left ventricles....

AI Technical Summary

Benefits of technology

[0043]The present invention enhances and improves the detection capabilities of implantable therapy and monitoring medical devices. Specifically, the invention may be implemented in subcutaneous or submuscular sensing where noise and interference distort signals. It can also be used in external monitors, including event recorders and Holter monitoring systems, as well as in the Holter analysis software that is used to analyze a Holter recording.

Problems solved by technology

Conduction defects affecting the A-V node response to a P-wave can cause the ventricles to beat too slowly, that is exhibit bradycardia, and not provide sufficient cardiac output.

Episodes of AF and AFL affect the atrial mechanical function and can have an effect on the ventricular heart rate that negatively affects cardiac output of the ventricles.

As described in commonly assigned U.S. Pat. No. 5,312,446 and in U.S. Pat. No. 4,947,858, both incorporated herein by reference, the externally worn ECG recorders have inherent limitations in the memory capacity for storing sampled ECG and EGM data.

Cost, size, power consumption, and the sheer volume of data over time have limited real time external Holter monitors to recording 24-hour or 48-hour segments or recording shorter segments.

The use of the externally worn Holter monitor coupled with skin electrodes is also inconvenient and uncomfortable to the patient.

The skin electrodes can work loose over time and with movement by the patient, and the loose electrodes generates electrical noise that is recorded with the EGM signal and makes its subsequent analysis difficult.

However, single chamber ICDs are more typically implanted to respond to single chamber tachyarrhythmias, and do not sense in both the atria and ventricles.

An AF or AFL episode can so affect the apparent RR intervals that are being monitored as to satisfy the VT / NF detection criteria, triggering the delivery of an inappropriate and possibly dangerous VT / VF therapy.

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